help: Japanese Knot Weed?

Japanese knot weed is a pernicious weed introduced by the Victorians
as a species plant / ornamental. It psreads undergound and quickly
takes over. Sounds bad eh? but it gets worse, the only method that
successfully eradicates it is to cut down the tall bamboo type stems
and cover the area with black polythene sheeting occluding light and
leave for up to two to three years....Im afraid that it seems there
are no known organicides that will kill the whole plant. Jim.